a) Field of the Invention
The invention refers to a device as well as to an evaluation procedure for the depth-selective, non-invasive detection of the blood flow and/or intra- and/or extra-corporeally flowing liquids in biological tissue.
b) Description of Related Art
The skin as a liminal organ between the human being and his environment has multiple functions. It accomplishes regulatory as well as immunological tasks and, last but not least, serves as a sense organ. In rough outlines, the skin is composed of the epidermis and the layer lying beneath it, called the corium, which consists of nerves, muscles and capillaries. The regulation of the microcirculation and the control of all other functions of the skin is realized through the interplay of these muscles, nerves and capillaries. A determination and control of the perfusion of the skin can now serve to detect perfusive variations and disturbances and to support a medical diagnosis. In the following a selection of the manifold applications is listed in catchwords:
Diagnosis of dermatological diseases, e.g. scleroderma, psoriasis PA1 Localization of manifestations of arteriosclerosis PA1 Assistance with the identification of cases of diabetic microangiopathy PA1 Observation of the arterial vasomotion PA1 Control of the functions of the sympathicus in the field of local anaesthesia PA1 Perfusion control with respect to transplantations, etc.
Laser Doppler systems have been used for decades for the diagnostic process in the field of dermal vessels. The most important restrictions of the conventional laser Doppler systems are their limited effective invasion depth and the analysis of isotropic signals. Thus, their use is limited to the measuring of the microcirculation of the skin, in the course of which a measuring volume of the size of a hemisphere with a maximum diameter of 1 mm may be analyzed. Furthermore, the devices for the investigation of the perfusion of the skin that have been used clinically up to now do not supply comparable measuring values. The users of these conventional systems, e.g. Flowmeter, have passed on to refer to the temporal reaction of the measuring values according to determined stimulations for the evaluation of the microcirculation.